Java数据库连接池实现

首先写一个读取本地数据库驱动，数据库用户名、数据库密码、连接数的类。

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package cn.cate.utils;import java.io.FileNotFoundException;import java.io.FileReader;import java.io.IOException;import java.util.Properties;public class PoolProperties {private Properties properties;private String driver;private String url;private String user;private String password;private int maxConn;private int minConn;public PoolProperties(){properties = new Properties();String path = getClass().getProtectionDomain().getCodeSource().getLocation().toString();path = path.substring(6, path.length());if (path.indexOf("WEB-INF") > 0) {      path = path.substring(0, path.indexOf("/WEB-INF") + 9) + "lib/";}else{      path = "d:";}try {this.properties.load(new FileReader(path + "db.pro"));}catch (FileNotFoundException e) {    e.printStackTrace();}catch (IOException e) {    e.printStackTrace();}this.setDriver(properties.getProperty("driver"));this.setUrl(properties.getProperty("url"));this.setUser(properties.getProperty("user"));this.setPassword(properties.getProperty("password"));this.setMaxConn(Integer.parseInt(properties.getProperty("maxConn")));this.setMinConn(Integer.parseInt(properties.getProperty("minConn")));}public Properties getProperties() {return properties;}public void setProperties(Properties properties) {this.properties = properties;}public String getDriver() {return driver;}public void setDriver(String driver) {this.driver = driver;}public String getUrl() {return url;}public void setUrl(String url) {this.url = url;}public String getUser() {return user;}public void setUser(String user) {this.user = user;}public String getPassword() {return password;}public void setPassword(String password) {this.password = password;}public int getMaxConn() {return maxConn;}public void setMaxConn(int maxConn) {this.maxConn = maxConn;}public int getMinConn() {return minConn;}public void setMinConn(int minConn) {this.minConn = minConn;}}

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db.pro的内容如下：

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driver=com.mysql.jdbc.Driver?? ? ? ?maxConn=10????? ? ? ?minConn=1???? ? ? ?url=jdbc:mysql://127.0.0.1:3306/cate???? ? ? ?user=root???? ? ? ?password=11111??

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然后定义一个数据库连接池：DBConnectionPool

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import java.sql.Connection;import java.sql.DriverManager;import java.sql.SQLException;import java.util.ArrayList;import java.util.Iterator;import java.util.List;/* * 此内部类定义了一个连接池，它能够根据要求创建连接，直到预定的最大连接数为止。 * 在返回连接给客户程序之前，它能够验证连接的有效性。 */public class DBConnectionPool {/* * 连接池 */private List<Connection> freeConnections = new ArrayList<Connection>();private Connection conn = null;private int connect = 0;     //使用的连接数private int maxConn;      //最大连接数private String driver;    //数据库驱动private String url;     //数据库连接地址private String user;     //用户名private String password;      //用户名public DBConnectionPool(String driver,String URL,String user,String password,int maxConn){this.driver = driver;this.url = URL;this.user = user;this.password = password;this.maxConn = maxConn;poolInfo();}/* * 显示准备创建连接池的信息 */private void poolInfo(){Connection conn = this.newConnection();freeConnections.add(conn);for(int i = 0;i < this.maxConn - 1;i++){Connection freeConn = conn;freeConnections.add(freeConn);}}/* * 用完，释放一个连接 */public synchronized void freeConnection(Connection conn){this.freeConnections.add(conn);this.connect--;}/* * 从连接池中获取一个可用连接，当无法从连接池中获取可用连接时，新创建一个连接 */public synchronized Connection getConnection(){if(this.freeConnections.size() > 0){/* * 当在连接池中取出一个连接后，删除此连接 */conn = this.freeConnections.get(0);this.freeConnections.remove(0);}/* * 当取出的连接为null时，递归调用自己，直到获得一个可用连接为止 */if(conn == null){conn = getConnection();}else{conn = newConnection();}if(this.maxConn == 0 || this.maxConn < this.connect){/* * 等待超过最大连接时 */conn = null;}if(conn != null){this.connect++;}return conn;}/* * 释放全部连接 */public synchronized void release(){Iterator<Connection> allConns = this.freeConnections.iterator();while(allConns.hasNext()){Connection conn = (Connection)allConns.next();try{if(null != conn){conn.close();}conn = null;}catch(SQLException e){e.printStackTrace();}}this.freeConnections.clear();}/* * 创建一个数据库连接对象 */private Connection newConnection(){try{Class.forName(driver);}catch(ClassNotFoundException e2){e2.printStackTrace();}try{conn = DriverManager.getConnection(url,user,password);}catch(SQLException e3){e3.printStackTrace();System.exit(0);}return conn;}}

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最后提供一个连接池的管理类：

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import java.sql.Connection;import java.util.Enumeration;import java.util.Hashtable;import cn.cate.utils.PoolProperties;/* * 连接池的管理类，负责读取配置连接池的文件，并创建连接池 * 从连接池中获取，释放连接 */public class DBConnectionManager {/* * 唯一数据库连接池管理实例类 * 使用单例模式创建 */private static DBConnectionManager instance;/* * 连接池的集合 */private Hashtable<String,DBConnectionPool> pools = new Hashtable<String,DBConnectionPool>();private static String poolName = "MYSQL_MZBA";      //连接池名字public static synchronized DBConnectionManager getInstance(){if(instance == null){instance = new DBConnectionManager();}return instance;}/* * 只允许内部实例化管理类 */private DBConnectionManager(){this.init();}/* * 加载驱动程序 */private void init(){PoolProperties poolProperties = new PoolProperties();DBConnectionPool pool = new DBConnectionPool(poolProperties.getDriver(), poolProperties.getUrl(), poolProperties.getUser(), poolProperties.getPassword(), poolProperties.getMaxConn());pools.put(poolName, pool);}/* * 根据连接池的名字得到一个连接 */public Connection getConnection(){DBConnectionPool pool = null;Connection conn = null;pool = pools.get(poolName);try{conn = pool.getConnection();}catch(Exception e){e.printStackTrace();}return conn;}/* * 释放一个连接 */public synchronized void freeConnection(Connection conn){DBConnectionPool pool = pools.get(poolName);if(pool != null){pool.freeConnection(conn);}}/* * 释放所有连接 */public synchronized void release(){Enumeration<DBConnectionPool> allpools = pools.elements();while(allpools.hasMoreElements()){DBConnectionPool pool = allpools.nextElement();if(pool != null){pool.release();}}pools.clear();}}